Chemical apparatus



Aug. 26, 1930. w, GLUUD ET AL 1,774,366

CHEMICAL APPARATUS Original Filed Nov. 1'?, 1926 lll Patented Aug. 26,1930 UNITED STATES PATENT OFFICE WILHELM GLUUD AND ROBERT SCHNFELDER, 0FDORTMUND-EVING, GERMANY,

ASSIGNORS, BY MESNE ASSIGNMENTS, TO FIRM: BERGWERKSVERBAND ZUR VER-WERTUNG VON SCHUTZRECHTEN DER KOHLENTECHNIK GESELLSCHAFT MIT IBE-SCHRNKTER HAFTUNG, OF DORTMUND-EVING, WESTPHALIA, GERMANY CHEMICALAPPARATUS Original application filed November 17, 1926, Serial No.148,982, and in Belgium May 25, 1926. Divided and this application filedJune 5, 1928.

The present invention refers to the eliminating of sulphuretted hydrogenfrom gases, in which an aqueous suspension, containing ferrous andferrie liydroxides or carbonates and Circulating in a closed circuit, isutilized, in a iirst step for washing the gas in order to tix thesulphur contained in the gas by means of compounds of iron present inthe wash liquid, and in a second step is then oxidized and regeneratedby treatment with the oxygen of the air, so that this liquid can beutilized again in the first step for washing the gas.

A process as above described is disclosed in our copending applicationfor patent of the United States Ser. No. 148,982, tiled November 17,1926.

One of the objects of the present invention is to provide means forobtaining in a highly concentrated form, that is, with a relativelysmall proportion of iron compounds, the sulphur which is present as amixture of sulphur and solid lcompounds of iron.

Another object of the invention when wash liquids containing an alkaliare used, in which case part of the sulphur is combined to form analkali thiosulfate, is to provide means for obtaining highlyconcentrated solutions of this alkali thiosulfate.

The essential characteristics of the invention, bv means of which theobjects indicated above are obtained, consist in thesuspension servingas the wash liquid having a very low concentration in iron, at the most2 per cent Fe, and circulating in a closed circuit for a suiiicientlylong time between the process of washing the gas and the process ofregeneration, the iron and alkali being replaced'as they are used up inthe course of the treatment.

The accompanying drawing shows diagrammatically in elevation an exampleof a plant embodying our invention.

The gases to be treated containing sulphuretted hydrogen, for example agaseous Serial No. 283,1 19.

distillation product from coke furnaces, retorts for illuminating gas,producers, etc., which are preferably, but not necessarily, submitted toa preliminary treatment for the elimination of cyanogen compounds, andin any case freed from tar, enter at the ordinary tei'nperature by apipe 1 into a vertical scrubber 2 provided with latticework or the likeand leave the latter by a pipe When the process is in regular working awash liquid is sprayed by a device 4 into the top of the scrubber andflows in the opposite direction to the gas. This liquid consists of anaqueous suspension of ferrous and vferrie hydroxides or carbonates,which may contain also in lsolution ferrous or ferrie salts, and mayalso carry with it either dissolved or in suspension the productsresulting from the treatment. The maximum amount of iron compounds inthe liquid must not exceed 2 per cent, of iron (Fe). Vhen the gas to bctreated initially contains ammonia, as is the case in the examplesmentioned, it is always possible to submit it before its entrance intothe scrubber to ,preliminary treatments by which its initial content inammonia is wholly or partially left iu the gas to be treated by thepresent process. 1n this case the wash liquid in the scrubber 2 absorbsthe ammonia of the gas and becomes alkaline. Even without thisassiunption as to the constitution of the gas, when it is desired forpurposes which will be explained later that the liquid should. bealkaline, satisfactory results can be obtained by adding the required.alkali to the wash liquid, for example, as a solution of sodiumcarbonate or sodium hydroxide, or, if ammonia is to he used as thealkali, in the form of a concentrated ammoniacal solution.

In consequence of the action of the compounds of ferrous and ferrieoxides of the suspension in the scrubber 2 on the gas containingsulphuretted hydrogen, the sulphur of the gas combines with the iron ina manner well known to every chemist, and is car- Atl ried in this formwith the wash liquid out of the scrubber Z and passes by a pipe 5provided at the bottom of the scrubber into a receptacle 6. The liquidis removed from this latter by a pump 8 through a suction pipe 7, anddelivered by a pipe 9' into the bottom ot a tower 10. At the bottom ofthis tower there is a perforated pipe 11 by means ot which compressedair is introduced. The air rises in a finely divided state through thecolumn of liquid which completely fills the tower and oxidizes thecompounds of iron and sulphur. The products of this oxidation are, as iswell known, free sulphur which remains in suspension in the liquid andhydroxides or carbonates of iron, which have been reoxidized to ferriehydroxides or carbonates, and in this form are suitable for repeatingthe washing and fixing of the sulphur in the scrubber 2, so that thewash liquid is again regenerated. lVhen an alkali, for example freeammonia, is present in the wash liquid, an alkali thiosulfate is formedin the oxidizing tower 10 from the sulphur present, that is. in the caseot ammonia, ammonium thiosulfate in solution. In other words, one partof the sulphur passes in the dissolved condit-ion into the wash liquid.The oxidized and regenerated wash liquid passes with the rest of theoxidizing air from the u per part ot the tower 10 by a suitably largepipe 12 into a sepa rating receptacle 13. This mixture ot liquid. ofmatters in suspension and of air forms a mass partly in a frothycondition and partly semi-liquid which is separated by settling in thereceptacle 13. The liquid constituents with the regenerated ferriecompounds in suspension and part of the sulphur fall to the bottom ofthe vessel and are delivered by a pipe 14 to the spraying device 4 atthe top ot the scrubber 2. In this way a closed circuit is provided torthe wash liquid through the scrubber Q. the oxidizing towel' l0 and theseparating receptacle 13. 'l`he rest ot the sulphur which isprecipitated in the wash liquid in the tower ltl and is transferred tothe receptacle 12, but is not returned to the scrubber Q. toi-ms amobile `foam floating on the surface ot the current ot liquid. rl`hisfoam. torlned principally of tinelv divided sulphur with which is mixeda portion ol' the lsolid compounds of iron. Hows from the receptacle l?)by a large pipe l5 into a depositing receptacle lo'. 'l`lle receptacle16 is preferably. as shown in the drawing` tapered towards the. base.like a funnel. and has at its lowest part a discharge tubulure 1T whichcan be closed. From this tubulure 1T a pipe 1S. which is also furnishedwith a valve leads to the receptacle 6. The small quantities of liquidwhich collect at the lower part ot the receptacle 1G can be returned bythe pipe 1S to the receptacle 6 before the foam deposited in 1li andthemass of sulphur and iron compounds mixed with the liquid have beendischarged by the tubulure 17. This mixture passes into a centrifuge 19in which the restot the liquid is eliminated by centrifugal action. Theexpelled liquid is carried by a pipe Q0 into the pipe 18 and thence intothe receptacle G. The separated out sulphur remains in the centrifuge19, mixed with a part of the compounds of iron (hydroxides. carbonatos),these latter being thus withdrawn from the cycle, and forms the crudesulphur which'is sent to its ulterior place of utilization and possiblyto a purifying device.

The remaining oxidizing air which is separated in the receptacle 13 isdischarged by a pipel 21 and joins the air escaping from the receptacle16 by a pipe Q2. and as this air carries with it a little ammonia fromContact with the ammoniaeal wash liquid in the oxidizing tower 10, it issent into an acid receptacle 23 to combine and recover the ammonia. Theair freed from ammonia escapes into the atmosphere by a discharge pipe24.

The iron extracted with the crude sulphur must naturally be replaced. Itis introduced most simply in the operation in the form of a solution offerrous or ferric salt, for ex ample sulfate ot iron (FeSO,+7 aq). Forthe preparation of this solution a receptacle 25 is used which isconnected to the receptacle 6 by a pipe Q6 provided with a closingmember. lVhen the process is carried out with an alkaline wash liquid,it is sufficient to pass the solution of iron salt directly from thereceptacle Q5 into the receptacle 6, where the dissolved iron salt istransformed under the action of the alkali present into solid hydroxideor carbonate insuspension. When the process is carried out in theabsence of alkali,

the transformation of the additional iron in solution into hydroxide orcarbonate of iron should be effected in the receptacle 25 by theaddition ot a suitable quantity of alkali.

At the commencement of the operation, the wash liquid in circulationonly contains, besides` the alkali that may be present (for exampleammonia present in the gas to be treated) a certain quantity ot ferroushydroxide or carbonate in suspension. but as yet no `sulphur. sulphur isextracted trom the gas by washing, fixed by the compounds of iron andfreed in consequence ot' the subsequent oxidation as sulphur insuspension. and in part also as an alkali thiosulfate in lsolution. (lfthis sulphur which the wash liquid carries with it meclnnlically a partonly is separated by a single passage through the receptacle lil. Therest ot the sulphur returns with the wash liquid into the closedcircuit. It is evident that in this manner by the frequent repetitionofthe cycle. the content ofthe wash liquid in sulphur is continuallyincreased. The content of the wash liquid in iron compounds, is, on theother hand, constantly maintained at ln the course ot the operation thetent of the iron also present in the wash liquid, A

the low concentration mentioned. In this manner, by a sufticlentlyprolonged or suiiiciently repeated circulation ot the wash liquid'between the processes ot' washing` the ,gas in the scrubberZandoxidationandregeneration in the tower l0, the content ot the washliquid in sulphur held in suspension is several times, for example aboutfive times or more, the couthis iron takingl the form ot compounds insuspension. Thus crude sulphur containing relatively small quantities ofsolid iron compounds is recovered in the receptacles i3 and 16.Obviously,also the consumption of the iron required in the process isreduced. This is due to the tact that from the commencement there isonly a feeble concentration of iron in the wash liquid in circulation.Consequently, eren when the .quantity of sulphur is Aa multiple of thequantity ot iron contained in the liquid, the accumulation of matter insuspension in this liquid remains within limits which do not injuriouslyati'ect the process. It is only when these conditions are fulfilled thatthe repeated circulation ot' the wash liquid can be effected for as longa time and as frequently as is necessary, accordingr to the y recedinvex ilanations` in order to obtain as a product a crude sulphur with ahigh content in sulphur, which obviously then allows the subsequenttreatment to be carried out very economically.

-When the operation is conducted by means of an alkaline liquid, it isalso possible, by the means described, in particular by the use for asutiiciently long time and repeated circulations of the wash liquid in aclosed circuit, to obtain highly concentrated alkali thiosulfatesolutions, that is to say to recover in dissolved form a considerablepart of the eliminated sulphur.

As the thiosulfate is present in solution, it is necessary for itsseparation and its treatnient to Withdraw at times part of the Washliquid in circulation from the process, or alternatively, to Withdrawand renew all ot it at one operation. ln this latter case it is possibleto recover easily also at once all the sulphur accumulated in the washliquid, tor example by filtration. Therefore, the treatment forobtaining' the thiosultate is also advantageous in many respects for theproduction of sulphur.

le wish it to be. understood that we do not desire to loe limited to theexact details ot construction and process shown and described forobvious modifications will occur to a person skilled in the art.

iipparatus tor carryingout the cyclic process for eliminatingsulphuretted hydrogen from gas comprising in combination a scrub ber torwashing the gas, a relatively highY oxidizing tower adapted to receivethe liquid from the scrubber at the bottom a column of liquid completelylillinplr and rising under Cit llo

